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Combining the results of base models to create a meta-model is one of the ensemble approaches known as stacking. In this study, stacking of five base learners, including eXtreme gradient boosting, random forest, feed-forward neural networks, generalized linear models with Lasso or Elastic Net regularization, and support vector machines, was used to study the spatial variation of Mn, Cd, Pb, and nitrate in Qom-Kahak Aquifers, Iran. The stacking strategy proved to be an effective substitute predictor for existing machine learning approaches due to its high accuracy and stability when compared to individual learners. Contrarily, there was not any best-performing base model for all of the involved parameters. For instance, in the case of cadmium, random forest produced the best results, with adjusted R2 and RMSE of 0.108 and 0.014, as opposed to 0.337 and 0.013 obtained by the stacking method. The Mn and Cd showed a tight link with phosphate by the redundancy analysis (RDA). This demonstrates the effect of phosphate fertilizers on agricultural operations. In order to analyze the causes of groundwater pollution, spatial methodologies can be used with multivariate analytic techniques, such as RDA, to help uncover hidden sources of contamination that would otherwise go undetected. Lead has a larger health risk than nitrate, according to the probabilistic health risk assessment, which found that 34.4% and 6.3% of the simulated values for children and adults, respectively, were higher than HQ = 1. Furthermore, cadmium exposure risk affected 84% of children and 47% of adults in the research area. [ABSTRACT FROM AUTHOR]

The importance of ecosystem services (ESs) has been widely recognized and studied since 2000. However, research on the interactions (synergies and trade-offs) among ESs and hotspots of ESs is limited. This study focused on the Asian Water Tower (AWT) region (17 countries) and assessed the importance of five critical ESs by four quantitative models, analyzed the interactions among ESs, and identified hotspots of ESs using hotspot analysis. The results showed that the areas with “high importance” of the composite ESs accounted for 6.3% of the AWT region, and they were distributed mainly in mountain and coastal areas. Additionally, high synergies among the five ESs were observed in areas with “high importance” of the composite ESs, whereas poor synergies among ESs were found in areas with “relatively high importance” of the composite ESs. Furthermore, a total of 132 hotspot basins (28.4% of the AWT region) of the composite ESs were identified, and 23.2% of the hotspot basins were areas with “highly and relatively highly synergistic” ESs. The results provide evidence-based support for setting ecosystem protection goals, achieving win-win ESs, and improving ecosystem management efficiency. Overall, this study can deepen the understanding of the interactions and hotspots of ESs in the AWT region. [ABSTRACT FROM AUTHOR]

Selenium (Se) is essential to human health, anti-cancer, possessing antioxidant, and antiviral properties. In this study, the spatial patterns of rice Se and their varying relationship with soil Se on a regional scale were studied using hot spot analysis for the agricultural soils in Guangxi. According to the hot and cold spot maps, rice Se correlates positively with soil Se in Guangxi agricultural soils. High rice Se accompanies high soil Se in the central part of Guangxi (e.g., Liuzhou, Laibin), and low rice Se is in line with low soil Se in the western part (e.g., Baise). However, the hot spot analysis maps indicate that southwestern Guangxi exhibits a special characteristic of low rice Se with high soil Se (e.g., Chongzuo). This special pattern is strongly associated with the high concentrations of Fe2O3 (ferromanganese nodules) in the carbonate rock area. The hot spot analysis proves useful in revealing the spatial patterns of rice Se in Guangxi and identifying the hidden patterns. [ABSTRACT FROM AUTHOR]

The characteristics of high concentrations or high activity levels of heavy metals, especially Cd, in soils caused by the pedogenesis of rocks are attracting increased attention. Carbonate rocks and black shales often coexist during geological deposition, but the risk characteristics of heavy metals are different after their weathering into the soil. The purpose of this study was to investigate the element concentrations of a naturally high background value area, to identify patterns of different risk areas, and to make recommendations for the safe usage of farmland. The results showed that, compared with the soil in the carbonate rock area, the soil in the black shale area was more acidified and most of the heavy metal elements were leached. Based on the soil pH value and the heavy metal concentrations, an identification method for land risk areas within naturally high background values was established, and land planning was carried out using this method. The exceeding rates of Cd in rice for the preferential protection area and strict control area were 0.0 and 50.0%, respectively. Therefore, in naturally high background area, the identified lithology can apply to maximize the use of farmland resources. This method provides a basis for preliminary ecological risk screening in naturally high background value areas using the results of the soil survey. A suggestion for the prevention and control of soil pollution in areas with naturally high background values was put forward. In carbonate rock areas, the soil should be closely monitored to prevent soil acidification. [ABSTRACT FROM AUTHOR]

The research of environmental geochemistry entered the big data era. Environmental big data is a kind of new method and thought, which brings both opportunities and challenges to GIS-based spatial analysis in geochemical studies. However, big data research in environmental geochemistry is still in its preliminary stage, and what practical problems can be solved still remain unclear. This short review paper briefly discusses the main problems and solutions of spatial analysis related to the big data in environmental geochemistry, with a focus on the development and applications of conventional GIS-based approaches as well as advanced spatial machine learning techniques. The topics discussed include probability distribution and data transformation, spatial structures and patterns, correlation and spatial relationships, data visualisation, spatial prediction, background and threshold, hot spots and spatial outliers as well as distinction of natural and anthropogenic factors. It is highlighted that the integration of spatial analysis on the GIS platform provides effective solutions to revealing the hidden spatial patterns and spatially varying relationships in environmental geochemistry, demonstrated by an example of cadmium concentrations in the topsoil of Northern Ireland through hot spot analysis. In the big data era, further studies should be more inclined to the integration and application of spatial machine learning techniques, as well as investigation on the temporal trends of environmental geochemical features. [ABSTRACT FROM AUTHOR]

COVID-19 pandemic provides an opportunity to investigate how a new and long-lasting threat affects public risk perception and social distancing behavior, which is important for pandemic risk management and recovery of the tertiary industry. We have found that the mechanism that perception decides behavior changes over time. At the beginning of the pandemic, risk directly shapes people's willingness of going out. But under a persistent threat, perception no longer plays the direct role of shape people's willingness. Instead, perception indirectly influences the willingness by shaping people's judgment about the necessity of traveling. Switching from direct to indirect influence, perception's effect is enlarged, which partially prevents people from returning to normal life even if the governmental ban is removed in a zero-COVID community. [ABSTRACT FROM AUTHOR]

This study investigated the influence of biochar on temperature, pH, organic matter (OM), seed germination index (GI), the fluorescent components of dissolved organic matter (DOM), and bioavailability of DTPA-extractable Cu and Cd during composting and analyzed the relation between DTPA-extractable metals with pH, OM, and the fluorescent components of DOM. Results showed that the addition of biochar shortened the thermophilic phase, reduced the pH at maturation period, accelerated the decomposition of OM, and raised GI. Besides, it promoted the formation of components with benzene ring in FA and HyI and the degradation of protein-like organic-matters in FA and HA, which was mainly related with the decrease of DTPA-extractable Cd and the increase of DTPA-extractable Cu. After composting, DTPA-extractable Cd in pile A and pile B were decreased by 37.15% and 27.54%, respectively, while the bioavailability of Cu in pile A and pile B was increased by 65.71% and 68.70%, respectively. All these findings demonstrate positive and negative impact produced by biochar into various heavy metals and the necessary of optimization measures with biochar in sediment composting. [ABSTRACT FROM AUTHOR]

The effects of biological factors including dissolved oxygen (DO), pH, carbon/nitrogen (C/N) and hydraulic retention times (HRT) on the performance of simultaneous nitrification and denitrification (SND) in a moving bed sequencing batch reactor (MBSBR) were investigated. A low DO was found to be advantageous to the SND in that nitrification was not inhibited, while pH and C/N ratio were shown to have positive effects on SND, and HRT needed to be controlled in a suitable range. A desirable SND efficiency was obtained at a DO of 2.5 mg L−1, pH of approximately 8.0, C/N ratio of 10 and HRT of 10 h in the MBSBR. High-throughput sequencing analysis showed that different operating conditions impacted microbial communities, resulting in different nitrogen removal mechanisms. Autotrophic and heterotrophic nitrification together contributed to the good nitrification performance, while denitrification was conducted by combined anoxic and aerobic processes. Furthermore, the results of principal component analyses (PCA) and the abundance of the predominant nitrification and denitrification genera both showed that DO and HRT might be regarded as the dominant variable factors influencing community structure analysis during SND, while the linear discriminant analysis (LDA) effect size (LEfSe) algorithm showed differences in abundance among the biofilm microbial communities with different DO. Overall, the results of this study improve our understanding of the bacterial community structure with different operating conditions in MBSBRs. [ABSTRACT FROM AUTHOR]

Purpose: Lead contamination is a prevalent issue affecting cities worldwide. Traditional fieldwork and laboratory analysis techniques can be time-consuming and costly. The purpose of this study was to evaluate the performance of ordinary cokriging (CK) when volume magnetic susceptibility (κ) is used as a co-variable for spatial interpolation of Pb in contaminated urban soils. Materials and methods: The study was conducted in contaminated urban soils of a former unregulated landfill site. A total of 76 surface samples (0–10 cm) were collected using a systematic sampling grid separated by 20-m intervals. Magnetic susceptibility measurements were taken at a higher density of 10-m intervals with 288 measurements. Thus, it was used as an auxiliary variable to predict Pb concentrations by the CK procedure with an aim to improve spatial interpolation of Pb. To determine the effectiveness of CK over the ordinary kriging (OK) procedure, the spatial density of samples was reduced prior to interpolation. A total of ~ 15%, 25%, 35%, and 50% of the Pb samples were randomly selected and reserved for validation. Omnidirectional semivariograms and covariograms were fitted using log-transformed data prior to interpolation. Results and discussion: Measurements of κ shared a significant relationship with Pb concentrations by the Spearman's Rho correlation analysis (rs = 0.676, p < 0.01). The effectiveness of the CK procedure over OK was determined using validation datasets. Statistically, the results showed that lnPb when its auxiliary relations with lnκ were used in CK had overall lower "root mean square error" (RMSE) and predicted lnPb values from the CK procedure had a higher r2 value with measured lnPb than OK. A model produced by the CK procedure with a reduced spatial density of 49 Pb points provided the more accurate map with a RMSE of 0.550 and an r2 value of 0.730, p < 0.01 level. Conclusions: This technique can potentially reduce fieldwork and soil analysis costs considerably. Measurements of Pb and κ must share a substantial level of spatial continuity to implement CK effectively. Where applicable, it can be used in the site-specific evaluation of hazard posed by Pb exposure to ecosystems, human health or water bodies in urban green spaces, roadside soils, allotments or brownfield sites. [ABSTRACT FROM AUTHOR]

A probabilistic risk assessment (PRA) using two-dimensional Monte Carlo analysis was followed to inspect the health risk associated with consumption of groundwater contaminated with nitrate in 26 wells located in rural areas of Malayer, Iran. In this technique, probability distributions were assigned to the concentration of nitrate in groundwater, daily intake rate of water, frequency of exposure together with total duration of exposure and the risk levels were worked out for adults and children, accordingly. In addition, four scenarios were investigated with an emphasis on the effect of correlation between exposure frequency and ingestion rate of water on estimated risk values. It was indicated that inclusion of correlation between parameters would influence the upper median quartile values of estimated risk however the total impact on the results of health risk assessment is not significant. Moreover, considering the 3rd quartile value of risk level for the total size of the study area, the risk level related to children was higher than that of the adults with respective values of 0.621 and 0.989. The spatial variation of nitrate was considered using ordinary kriging and a novel combined method of random forest and spatial proximity as covariate. It was concluded that the predictions made by ordinary kriging were more accurate than the random forest technique which can be attributed to the small data sets used in this research. [ABSTRACT FROM AUTHOR]

Purpose: Cd-contaminated soil is a common environmental problem. Stabilization is an effective way of in situ remediation for Cd contamination in soils, but there is a lack of information about the influences of the amendments on soil ecosystems and Cd uptake by crops, especially under field conditions. In this study, surface-modified nano-silica (SMNS) was used to stabilize a Cd-contaminated soil under field condition within one year. Materials and methods: SMNS was mixed with Cd-contaminated soil at the dosage of 0%, 0.2%, 0.4%, 0.6%, 0.8%, and 1%, respectively. After that, corn and wheat were sown within one year. DTPA extraction and sequential extraction were used to evaluate stabilization efficiency of SMNS to Cd. The influences of SMNS on crop yield, soil enzyme activities, and Cd accumulation in crops were also analyzed. Results and discussion: The DTPA-extractable Cd in soil was reduced by 61.14% when the dosage of SMNS was 1%. SMNS transferred Cd to more stable fractions, with the organic-bound and residual Cd increased 148.11% and 90.52%, respectively. The addition of SMNS decreased soil dehydrogenase slightly, but its influences on soil urease, catalase, and yields of corn and wheat were negligible. More importantly, at the dosage of 1%, SMNS reduced 42.87% and 47.95% of Cd contents in corn and wheat grains, respectively. Conclusions: SMNS was effective in reducing the mobility of Cd in contaminated soils. These results suggest that SMNS has a great potential in the remediation of Cd-contaminated agricultural soils. [ABSTRACT FROM AUTHOR]

Insufficient information on the link between health data and geology in developing countries is a major barrier to identify sources of some emerging public health problems. A total of 2868 soil samples were collected from field sheet 0503B in Ghana to evaluate the concentrations and distributions of trace elements and their effects on human health. The samples were sieved to < 106 µm fraction and analysed for elements, As, Ba, K, Zn, Co, Cr, Cu, Mn, Ni, Pb, Mg and Fe by XRF technique and Au by fire assay method. The study identified disparities in averages of As, Cr, Fe and Mg, which resulted in enrichment and deficiencies when compared with the worldwide background average. The measured averages for As and Cr were 17.27 mg/kg and 89.25 mg/kg, respectively, for the entire area. Both averages exceeded the worldwide background values of 10 mg/kg and 8 mg/kg of As and Cr. The four traditional towns with varied activities recorded As concentrations ranging from 6.11 mg/kg at Samreboi, 16.29 mg/kg at Asankragwa, 17.42 mg/kg at Akropong and 25.99 mg/kg at Bogoso. Principal component analysis revealed a good association among Ba, Cr, Cu, Fe, K, Ni, Pb and Zn in Group 1, and their main source was interpreted as the underlying geology. Arsenic, Cr and Mg in Group 2 show a relatively weak correlation, and their sources were ascribed to a combination of geologic and anthropogenic sources. Gold had a good correlation with As, which was associated with the hydrothermal veins in the underlying rocks. The spatial plots generated from transformed soil data by Getis Ord Gi* treatments were visual methods to clearly identify geographically the hotspots and coldspots of elements that cause diseases. [ABSTRACT FROM AUTHOR]

Anaerobic biological phosphorus removal has proposed a new direction for the removal of phosphorus from wastewater, and the discovery of phosphate reduction makes people have a more comprehensive understanding of microbial phosphorus cycling. Here, from the perspective of thermodynamics, the bioreduction reaction of phosphate was analyzed and its mechanism was discussed. The research progress of phosphate reduction and the application prospects of anaerobic biological phosphorus removal from wastewater were introduced, pointing out the situation and guiding the further research in this field. [ABSTRACT FROM AUTHOR]

The study aims to seek the dietary strategies to reduce the bioaccessibility of Cd and As in contaminated rice. A total of 12 selected food matrices were assayed by using the in vitro gastrointestinal digestion models. The results showed that tomato, carrot, water spinach, and spinach reduced the solubility of Cd by 45-78%, 50-71%, 53-70%, and 45-71%, respectively. Meanwhile, tomato, carrot, potato, and sweet potato reduced the solubility of As by 53-79%, 50-80%, 40-71%, and 36-76% in aqueous solution, respectively. In both gastric and gastrointestinal phases, Cd and As bioaccessibility decreased as the amount (100, 200, or 400 mg) of food matrices increased (except for As in water spinach). These results suggested that the uses of some foodstuffs may be a good dietary strategy to reduce Cd and As bioaccessibility, although in vivo studies are required to confirm their suitability. [ABSTRACT FROM AUTHOR]

Diffusive gradients in thin films technique (DGT) is a dynamically passive sampling technique which has been applied increasingly to the environmental monitoring field. In the preliminary period, the DGT with zirconium hydroxide-silver iodide as the binding phase (ZrO-AgI DGT) has been developed for the determination of sulfide (S(II)). On this basis, this paper developed its determination method for inorganic arsenite (As(III)) to further realize the simultaneous and high-resolution measurements of labile inorganic As and S(II) in sediments. ZrO-AgI binding gel had a strong ability in adsorbing and fixing As(III), showing a linear increase in the initial 12.5 min. After saturation of S(II) on ZrO-AgI binding gel, the adsorption rate and adsorption capacity of As(III) reduced by 8 and 14%, respectively. A stable elution rate (89.1 ± 2.2%) was obtained by extraction of As(III) on the binding gel using a mixture solution of 1.0 M NaOH and 1.0 M H2O2 (1:1). The DGT capacity of As(III) determined by the ZrO-AgI DGT was 23.6 μg cm−2. DGT uptakes of As(III) were independent of pH (4.0-9.0) and ionic strength (0.01-100 mM), and they did not interfere with each other during the uptake process. Simultaneous measurements of labile As and S(II) in four sediment cores of Taihu Lake (China) with ZrO-AgI DGT showed that they had similarly vertical distributions in the top 16-mm layer in one core and in the whole profile up to the 35 mm depth in two cores. It likely reflected a simultaneous release of As and S(II) in sediments by synchronous reduction of As-hosted oxidized iron and sulfate, respectively. The simultaneous decreases of labile As and S(II) from their co-precipitation (e.g., As2S3) were not obvious in deeper sediment layer through the measurement with ZrO-AgI DGT. [ABSTRACT FROM AUTHOR]

The environmental deterioration is in a grave situation, and it is urgent to restore the environment. Biochar is a carbon-rich pyrolysis product of feedstock, which has aroused extensive concern due to its broad application potential for getting rid of pollutants and rehabilitating environment. This review generalizes three aspects on biochar, including production and properties, applications and mechanisms, and its modifications. Firstly, the production and characteristics have been summarized, because the practical applications of biochar are highly related to the special characteristics of biochar. Secondly, this paper outlines the latest applications of biochar for environmental remediation, and further provides a critical review on the application mechanisms in environmental restoration. Thirdly, the modification methods and applications of modified biochar are summarized, and all of the ways can be classified into two types: pretreatment of feedstock and modification of primitive biochar. Furthermore, the possible improvements and outlooks of applying biochar in environmental remediation are proposed. This review provides useful information for the application of biochar in environmental restoration. [ABSTRACT FROM AUTHOR]

The release of arsenic (As) from sediments poses a risk to human health especially at high pH levels. Despite this, the distribution and kinetic response of mobile As remains unclear under varying pH conditions. In this study, a microcosm incubation experiment was performed, using sediment cores in combination with dialysis (Peeper) and thin film diffusive gradients (DGT), to investigate the distributions of mobile As (soluble As in pore water and DGT-labile As) at high vertical resolutions (2-4 mm). Results show that the concentrations of soluble As present in the water column increased 1.5-fold with an increase in pH from 5.4 to 11.2. Both soluble As in pore water and DGT-labile As exhibited stable low-level distributions in the uppermost layer beneath the sediment-water interface, followed by increasing concentration distribution with decreasing layers to middle depths. The mean concentrations of mobile As species increased with increased water pH in both sediment profiles and with upward diffusion gradients, showing a 0.2-fold increase of soluble As in the top 20-mm layer and a 0.6-fold increase in deeper 20-52-mm layers, while DGT-labile As showed a 1.0- and 1.1-fold increase in these two layers, respectively. Modeling of DGT-induced flux in sediments (DIFS) showed that the desorption rate constant increased more rapidly than the absorption rate constant, resulting in the increased availability of solid As pools, therefore resupplying the soluble As in pore water from sediments. [ABSTRACT FROM AUTHOR]

Much attention has been paid to the availability of arsenic (As) in soils, while few studies were carried out on the comparison between the dry and flooded soils using different methods. In this study, chemical sequential extraction and diffusive gradients in thin films (DGT) techniques were employed to study the availability of As in soils amended with a range of exogenous As followed by one-year incubation under dry and flooded conditions, respectively. The results showed that the proportions of available solid As pools, including non-specifically adsorbed As (F1) and specifically adsorbed As (F2), had consistent increases with the increase of As amendment. The concentration of DGT-measured As ( C ) and dissolved As in soil solution ( C ) also increased up to 2573 (dry) and 1823 (flooded) times and 4067 (dry) and 3105 (flooded) times of the control, respectively, while their ratios ( R) showing the extent of C sustained from solid resupply decreased from 0.17 to 0.10 (dry) and 0.35 to 0.21 (flooded). Modelling with DGT-induced fluxes in soils (DIFS) further showed an increase of T (the characteristic time to reach equilibrium from DGT perturbation) and decreases of desorption and adsorption rate constants ( k and k ) with the increase of As amendment, reflecting a decrease in kinetic exchange rate of As between available solid As pool and soil solution. The flooded soils had greater values of R, k and k and lower value of T in comparison with the dry soils, indicating a greater availability of As under the flooded condition. [ABSTRACT FROM AUTHOR]

A systematic investigation into cadmium (Cd) and lead (Pb) concentrations and their oral bioaccessibility in market vegetables in the Pearl River Delta region were carried out to assess their potential health risks to local residents. The average concentrations of Cd and Pb in six species of fresh vegetables varied within 0.09-37.7 and 2.3-43.4 μg kg, respectively. Cadmium and Pb bioaccessibility were 35-66 % and 20-51 % in the raw vegetables, respectively, and found to be significantly higher than the cooked vegetables with 34-64 % for Cd and 11-48 % for Pb. The results indicated that Cd bioaccessibility was higher in the gastric phase and Pb bioaccessibility was higher in the small intestinal phase (except for fruit vegetables). Cooking slightly reduced the total concentrations and bioaccessibility of Cd and Pb in all vegetables. The bioaccessible estimated daily intakes of Cd and Pb from vegetables were far below the tolerable limits. [ABSTRACT FROM AUTHOR]

With the development of researches, the treatments of wastewater have reached a certain level. Whereas, heavy metals in wastewater cause special concern in recent times due to their recalcitrance and persistence in the environment. Therefore, it is important to get rid of the heavy metals in wastewater. The previous studies have provided many alternative processes in removing heavy metals from wastewater. This paper reviews the recent developments and various methods for the removal of heavy metals from wastewater. It also evaluates the advantages and limitations in application of these techniques. A particular focus is given to innovative removal processes including adsorption on abiological adsorbents, biosorption, and photocatalysis. Because these processes have leaded the new trends and attracted more and more researches in removing heavy metals from wastewater due to their high efficency, pluripotency and availability in a copious amount. In general, the applicability, characteristic of wastewater, cost-effectiveness, and plant simplicity are the key factors in selecting the most suitable method for the contaminated wastewater. [ABSTRACT FROM AUTHOR]

Outliers are classified as global outliers and spatial outliers. Up to now, there is little information about the outliers especially the spatial outliers and their influence on the spatial structure modeling of soil properties. A total of 537 soil samples were collected based on a 30 × 30 m grid in a permanent dairy farm in southeast Ireland. Graphic methods of histogram and box plot combined with Moran's I were applied to detect the outliers of soil phosphorus (P). Sixteen outliers (5 global outliers and 11 spatial outliers) of soil P were found in the study area. Compared to the raw data, the data with global outliers excluded always had the larger global Moran's I value indicating a stronger spatial autocorrelation. Clear spatial clusters (High-High and Low-Low clusters) were observed based on local Moran's I. The High-High spatial clusters were located around the main farm yard and near the traffic route due to more intensive management by farmers. The Low-Low spatial clusters were mainly close to the river. For these areas, P fertilizer or slurry should be applied for healthy grass growth. The dataset with outliers excluded had a reliable semi-variogram model with a low nugget/sill ratio (32.4 %), which was closed to its corresponding transformed data (30.5 %). The cross-validation results revealed that the dataset without outliers had the strongest linear regression model ( r = 0.768), indicating that the outliers played an important role in the spatial structure modeling. [ABSTRACT FROM AUTHOR]

This paper is purposed to detect the spatial laws of gastric cancer in the rapid urbanization area and analyze relationships between gastric cancer and urbanization. Gastric cancer incidence data in Xiamen between 2006 and 2009 was collected from Xiamen CDC (Centre of Disease Control and Prevention). Urbanization age of Xiamen Island was calculated from remote images and terrain maps. Analysis results showed that 995 gastric cancer cases, accounting for 61.64 % was in Xiamen island, compared with 619 cases, accounting for 38.36 % outside. The average gastric cancer incidence was 32.98/1000,000 in Xiamen Island, compared to 16.13/1000,000 outside. The top ten sub-districts of gastric cancer all located in Xiamen Island, and urban areas have as more than twice gastric cancer incidence as rural area, with 28.62/100,000. The most likely spatial cluster of gastric cancer was Xiamen Island. Correlation analysis results indicated the urbanization age and spatial cluster degree had a significantly positive correlation relationship. Rapid urbanization in Xiamen changed the environment, namely acquired factors including land use change, air-water-soil pollution, less activity, electromagnetic radiation and contaminated sea foods. These are risk factors of gastric cancer. This research indicated that Xiamen Island was prevalent of gastric cancer with a positive correlation with urbanization age. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the pollution profiles of various typical brominated flame retardants in water and surface sediment near a typical electronic waste dismantling region in southern China. We found that polybrominated diphenyl ethers (PBDEs), 2,4,6-tribromophenol (TBP), pentabromophenol (PeBP), tetrabromobisphenol A (TBBPA), and bisphenol A (BPA) were ubiquitous in the water and sediment samples collected in the study region. In water, ΣPBDEs (sum of all 20 PBDE congeners studied except BDE-209, which was below the detection limit) levels ranged from 0.31 to 8.9 × 10 ng L. TBP, PeBP, TBBPA, and BPA concentrations in the water samples ranged from not being detectable (nd-under the detection limit) to 3.2 × 10 (TBP), from nd to 37 (PeBP), from nd to 9.2 × 10 (TBBPA) and from nd-8.6 × 10 ng L (BPA). In sediment, ΣPBDEs ranged from nd to 5.6 × 10 ng g, while BDE-209 was the predominant congener, with a range of nd to 3.5 × 10 ng g. Tri- to hepta-BDE concentrations were significantly ( p < 0.01) correlated with each other, except for BDE-71 and BDE-183, and octa- to nona-BDEs concentrations were significantly ( p < 0.05) correlated with each other, except for BDE-208. BDE-209 was not significantly correlated with tri- to nona-BDEs. Risk assessments indicated that the water and sediment across the sampling sites posed no estrogenic risk. However, different eco-toxicity risk degrees at three trophic levels did exist at most sampling sites. [ABSTRACT FROM AUTHOR]

On the basis of achieving shortcut nitrification in a lab-scale SBR, the effects of constant pH and unsteady pH at different free ammonia concentrations on shortcut nitrification for landfill leachate treatment was investigated. The results indicate that under the condition of DO of 0.5 ± 0.2 mg/L and temperature of 30 ± 2 °C, the absolute value of nitrite accumulation increased significantly with the increase in free ammonia (FA) concentration from 5.30 to 48.67 mg/L; however, the nitrite accumulation rate remained almost constant at a constant pH of 8.0 ± 0.1. Ammonia oxidation and the nitrite accumulation become slow with the pH decreased from 8.0 ± 0.1 to 7.5 ± 0.2, and the activities of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were severely inhibited when the pH further decreased to 6.5. More importantly, this study confirmed that the pH decrease from 8.0 to 6.5 within a short time exhibited significant negative effect on the ammonia oxidation rather than the FA concentration. [ABSTRACT FROM AUTHOR]

Purpose: Reclaimed coastal wetlands are an important land resource because of the shortage of cultivated land in coastal areas, but few studies have focused on contamination of heavy metals in reclaimed agricultural soils, especially in soils that have experienced long-term agricultural activities. This study was carried out in Chongming Dongtan of the Yangtze Estuary, which has undergone large-scale reclamation activities, with the aim of determining the concentrations and spatial distributions of heavy metals in different reclaimed zones. Materials and methods: In this study, 50 soil samples were collected in the study area, which was divided into three zones based on the history of reclamation (post-1998, 1990s, and 1960s) and intertidal flats. Soil metals (Al, Fe, Mn, Cu, Cr, Ni, Zn, and Pb), soil pH, Eh, salinity, soil organic matter (SOM), and grain sizes were analyzed. Correlation analysis and factor analysis were employed to extract the main influencing factors on heavy metals in reclaimed soils. Al-normalization was used to remove the grain-size effect. The enrichment ratio (ER) was applied to reflect the chronological change of heavy metals after reclamation. Inverse distance weighted (IDW) interpolation was used to create spatial distribution maps of the measured heavy metals. Results and discussion: There were significant positive correlations ( p < 0.01) between the fine particle fractions (<20 μm) of soils and metal concentrations. Background deposition of metals in the study area increased relative to the reference values of each zone during the last 50 years. In zone post-1998, the concentrations of Cu, Zn, and Pb after reclamation were lower than those before reclamation, but not for Cr; in zone 1960s and 1990s, the concentrations of Cu, Cr, Zn, and Pb were higher than those before reclamation. In all the zones, the reclamation process had little impact on the mobilization of Ni. Our results showed that after Al-normalization, the differences of heavy metal concentrations between different zones and their spatial distribution patterns were due to the combined effects of both background deposition and anthropogenic processes, particularly in zone 1960s. Conclusions: The current heavy metal concentrations were mainly determined by the deposition background in Chongming Dongtan, but the reclamation history had certain effects on heavy metal concentrations in the reclaimed soils. The desalination leaching effect on heavy metals was mainly found for soils with short-term reclamation (zone post-1998), but with longer reclamation history (like zone 1960s and 1990s); long-term agricultural activities had greatly influenced the concentrations of heavy metals. [ABSTRACT FROM AUTHOR]

This paper provides an overview of the principle and latest development of the diffusive gradients in thin films (DGT) technology and its applications in environmental studies with a focus on bioavailability assessment of phosphorus and metals in sediments and soils. Compared with conventional methods, DGT, as a passive sampling method, has significant advantages: in situ measurement, time averaged concentrations and high spatial resolution. The in situ measurement avoids artificial influences including contamination of samples and sample treatment which may change the forms of chemicals. The time averaged concentration reflects representative measurement over a period of time. The high-resolution information captures the biogeochemical heterogeneity of elements of interest distributed in microenvironments, such as in the rhizosphere and the vicinity of the sediment-water interface. Moreover, DGT is a dynamic technique which simultaneously considers the diffusion of solutes and their kinetic resupply from the solid phases. All the advantages of DGT significantly promote the collection of 'true' information of the bioavailable or labile forms of chemicals in the environment. DGT provides potential for applications in agriculture, environmental monitoring and the mining industry. However, the applications are still at the early testing stage. Further studies are needed to properly interpret the DGT-measured results under complex environmental conditions, and standard procedures and guideline values based on DGT are required to pave the way for its routine applications in environmental monitoring. [ABSTRACT FROM AUTHOR]

Eutrophication of lakes and reservoirs has become a worldwide environmental problem, and nitrogen (N) has been recognized as one of the key factors responsible for eutrophication. Nitrogen adsorbed on sediments may be released via chemical and biological processes under changing environmental conditions. Spatial distributions of concentrations of ammonia nitrogen (NH-N), nitrate nitrogen (NO-N) and total nitrogen (TN) were investigated in sediments and overlying water of Dongting Lake, the second largest freshwater lake in China. The concentration of TN in the sediments exhibited strong spatial variation with relatively high values in the eastern part and relatively low values in the southern part of the lake. The TN concentration in the water of different regions of Dongting Lake was affected by the internal load of sediment N. The vertical distribution of TN in sediment cores showed a decreasing trend with an increase in depth. Concentrations of NH-N in the sediment cores decreased with the depth increase until 6-8 cm and then increased slowly. However, concentrations of NO-N in the sediment cores showed an opposite trend from those of NH-N. A kinetic release experiment of NH-N showed that the maximum release rate occurred in the first 5 min and the amount of NH-N release reached 77.93-86.34 % of the total amount in 0-10 min. The release of NH-N in the surface sediments of Dongting Lake fits a first-order kinetics function. [ABSTRACT FROM AUTHOR]

The Institute of Geochemistry, Chinese Academy of Sciences (IGCAS) and the International Medical Geology Association (IMGA) hosted the conference with the support of Guangzhou University, China University of Geosciences (Wuhan), National University of Ireland, Galway, and Guizhou Medical University. This special issue collected 14 research papers and 1 review paper, which covered the topics of water pollution, soil pollution, and human exposure and health effects. [Extracted from the article]

Soils in the vicinity of roads are recipients of contaminants from traffic emissions. In order to obtain a better understanding of the impacts of traffic on soils, a total of 225 surface soil samples were collected from an urban park (Phoenix Park, Dublin, Ireland) in a grid system. Metal (Pb, Cu and Zn) concentrations were determined using a portable X-ray fluorescence analyzer. Strong spatial variations for the concentrations of Pb, Cu and Zn were observed. The spatial distribution maps created using geographical information system techniques revealed elevated metal concentrations close to the main traffic route in the park. The relationships between the accumulation of Pb, Cu and Zn in the roadside soils and the distance from the road were well fitted with an exponential model. Elevated metal concentrations from traffic pollution extended to a distance of approximately 40 m from the roadside. The results of this study provide useful information for the management of urban parks particularly in relation to policies aimed at reducing the impact of traffic related pollution on soils. [ABSTRACT FROM AUTHOR]

Copper (Cu) is one of the essential elements for plant growth, while excessive Cu in soils has potential environmental risks. There is little information on spatial variation of Cu in practical paddy fields. This is now important for appropriate agricultural management. The spatial patterns of Cu, its fractions in soils, and its concentrations in rice were investigated in a typical rice production region-Wenling of southeastern China. A total of 96 pairs of rice grain and soil samples (0-15 cm) were collected. The total concentration of Cu and its fractions were very variable, with large skewness, kurtosis, and coefficient of variation (CV) values. Compared to the guideline value (50 mg kg), Cu pollution in paddy fields was observed in the study area. All the measured Cu concentrations in rice were lower than 10 mg kg, suggesting that they remained at a safe level. Spatial analyses including Moran's I index and geostatistics results indicated that high-high spatial patterns for both Cu in soils and rice were found in the northwest part, which was mainly related to industrial and E-waste dismantling activities. The low-low spatial patterns of Cu in the soil-rice system were located in the south part of study area. The cross-correlogram results indicated that Cu concentration in rice was significantly spatially correlated with total Cu in soils, its fractions, and soil organic matter (SOM), but significantly negatively correlated with pH and electrical conductivity (EC). Most of the selected variables had a clear spatial correlation range with Cu in rice. The ranges of significant spatial correlation ( p < 0.05) could be obtained and further used for dividing agricultural management zones. [ABSTRACT FROM AUTHOR]

To reveal the succession procedure of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) community structure in sequencing biofilm batch reactor (SBBR), the molecular biological techniques of denaturing gradient gel electrophoresis (DGGE), cloning, and real-time PCR were applied. DGGE showed that the structural diversity of the bacterial community increased during the biofilm formation period, and some kinds of populations had been highly preponderant consistently. The results of cloning and sequencing revealed that Nitrosomonas was the dominant species. The real-time PCR analysis indicated that the amount of the AOB increased significantly after the cultivation period, and the NOB gradually decreased. The AOB content on the 25th day was 17 times that of the 6th day. It also showed the biofilm formed successfully with accumulating nitrite and prepared to achieve the achievement of simultaneous nitrification and denitrification in SBBR. Furthermore, the ammonia-oxidizing rate was in correspondence with the NH-N removal efficiency. [ABSTRACT FROM AUTHOR]

As one of the largest economical hubs in southwestern China, Chengdu is witnessing fast urbanization characterized by rapid urban sprawl, population growth, infrastructural construction, and motorization. However, this rapid urbanization may lead to environmental degradation, placing human health at risk. In this study, toxic metals in road dust and roadside soil are used as proxies to illustrate environmental changes of Chengdu. In August 2009, 133 dust and 132 soil samples were collected from the first, second and third ring roads, along which areas have urbanized for different times. By means of a portable X-ray fluorescence analyzer, concentrations of Pb, Zn and Cu in the samples were determined. The results indicate that the concentrations and contamination levels of Pb, Zn and Cu in dust declined significantly from the first to the third ring roads, paralleling the decreasing trends in traffic and building densities from the first to the third ring roads. However, concentrations of the three elements in roadside soil were relatively stable among the roads. These data may suggest that the metals in road dust can be used as proxies to demonstrate environmental degradation during the urbanization of Chengdu, while concentrations of the metals in roadside soil are affected more by natural factors (e.g., background concentrations, precipitation, and distance to road) than by anthropogenic factors (e.g., traffic and building densities). Furthermore, compared to Pb concentrations measured in the 1990s, Pb concentrations in road dust have been reduced most likely owing to the exclusion of leaded petrol since 2000. Similar situations may be found in many other cities that are experiencing fast urbanization. [ABSTRACT FROM AUTHOR]

Assessing the environmental risk of metal contamination in soils requires the determination of both total (TCs) and bioavailable (BCs) element concentrations. A total of 200 surface (0-10 cm) soil samples were collected from an urban sports ground (South Park) in Galway, Ireland, a former landfill and dumping site, which is currently under remediation. The potential BCs of metals were measured using ethylene-diamine-tetra-acetic acid (EDTA) extraction followed by inductively coupled plasma-optical emission spectrometry analysis, while the TCs were determined using portable X-ray fluorescence spectrometry. It was found that Zn was primarily present in the insoluble residue (EDTA un-extractable) fraction in soils, with the median ratio of BCs/TCs 0.27. However, Pb and Cu had higher ratios of BCs/TCs (median values of 0.60 and 0.39, respectively) suggesting that they are potentially more bioavailable in the soils. The spatial distribution maps showed that both TCs and BCs for Cu, Pb and Zn in the study area were spatially heterogeneous. It was found that the BCs exhibited generally similar spatial patterns as their TCs of Cu, Pb and Zn: high values were mainly located in the west, north-east and south-east portions of the study area, where only a thin layer of topsoil existed. It was recommended that the current remediation action for this site needs to be carried out on an urgent basis. [ABSTRACT FROM AUTHOR]

The phosphorus index (PI) can be used to effectively identify areas with high risks of phosphorus losses. Manures and fertilizers are important source factors for the establishment of the PI system. An artificial precipitation experiment was performed to evaluate phosphorus losses with the applications of different types of fertilizers and manures. The results showed that the total phosphorus (TP) losses in runoff followed the order of ammonium phosphate monobasic (NHHPO), ammonium hydrogen phosphate ((NH)HPO), monobasic potassium phosphate (KHPO), chicken manure, and cattle manure with surface application of these fertilizers and manures. The order was slightly changed to NHHPO, KHPO, (NH)HPO, chicken manure, and cattle manure with incorporation application under the same rainfall condition. Both the methods and the rate of manure application can affect the amounts of phosphorus in water and particles of runoff. More than 90 % of TP in runoff were lost through suspended particles. Manure application had a significant contribution to the P load in runoff. [ABSTRACT FROM AUTHOR]

The effects of antecedent soil moisture on losses of rare earth elements (REEs) and phosphorus (P) in runoff were evaluated through a simulated rainfall experiment at the rate of 83 mm h. The results revealed that antecedent moisture was a significant factor affecting the amounts of REE and P losses. It was observed that most REEs and P transported with sediments in the runoff. There was a significant correlation between the total amounts of REE losses and those of P losses in the runoff. The optimal antecedent moisture for minimization of losses for REEs ranged from 10.19 to 11.17% and it was 10.91% for P. [ABSTRACT FROM AUTHOR]

Purpose: The single-step sodium hydroxide-ethylenediaminetetraacetic acid (NaOH-EDTA) extraction is currently the most common preparation technique for the measurement of organic phosphorus (P) composition in sediments using solution P nuclear magnetic resonance (NMR). In this study, detailed investigations were conducted to evaluate the performance of this technique, with an objective of finding an optimal procedure for the measurement of sediment organic P. Materials and methods: A single-step extraction with NaOH-EDTA was investigated on two types of sediment, i.e., Fe/Al-rich sediment and calcareous sediment. The influence of different sediment preparation methods, NaOH-EDTA compositions, solid:solution ratios, extraction time, pre-concentration techniques, and NMR sample frozen storage time on P extraction and solution P NMR analysis were investigated. Results and discussion: Both air- and freeze-drying increased organic P extraction for the calcareous sediment. An extraction time of 16 h was sufficient for quantitative recovery of extracted organic P for both Fe/Al-rich and calcareous sediments. The use of a 1:8 solid:solution ratio achieved stronger NMR signals and greater P diversity than the use of a 1:20 ratio. Extraction of the two sediments with 0.25 NaOH-50 mM EDTA favored P NMR detection by reducing the relaxation times required and the risk of organic P degradation compared to the use of stronger NaOH-EDTA solutions. Rotary evaporation was a better technique for pre-concentration of the NaOH-EDTA extracts than freeze drying. The concentrated extracts could be preserved by freezing (−20 °C) for at least 2 months. Conclusions: An optimized procedure was developed based on these investigations, including freeze-drying of fresh sediments, extraction with 0.25 M NaOH-50 mM EDTA for 16 h using a solid:solution ratio of 1:8, pre-concentration of the extract to the level of ∼10 times of its original concentration using rotary evaporation, and storage of the NMR sample at −20 °C until P NMR analysis. [ABSTRACT FROM AUTHOR]

Heavy metals in urban soils continue to attract attention because of their potential long-term effects on human health. During a previous investigation of urban soils in Galway City, Ireland, a pollution hotspot of Pb, Cu, Zn and As was identified in the sports ground of South Park in the Claddagh. The sports ground was formerly a rubbish dumping site for both municipal and industrial wastes. In the present study, a portable X-ray fluorescence (PXRF) analyser was used to obtain rapid in-situ elemental analyses of the topsoil (depth: about 5–10 cm) at 200 locations on a 20 × 20-m grid in South Park. Extremely high values of the pollutants were found, with maximum values of Pb, Zn, Cu and As of 10,297, 24,716, 2224 and 744 mg/kg soil, respectively. High values occur particularly where the topsoil cover is thin, whereas lower values were found in areas where imported topsoil covers the polluted substrate. Geographic Information Systems (GIS) techniques were applied to the dataset to create elemental spatial distribution maps, three-dimensional images and interpretive hazard maps of the pollutants in the study area. Immediate action to remediate the contaminated topsoil is recommended to safeguard the health of children who play at the sports ground. [ABSTRACT FROM AUTHOR]

Presents a paper which attempts to demonstrate the application of geostatistics in spatial analysis of environmental geochemcial, using the copper content in sediments of the Yangtze River. Details on the spatial distribution pattern of an element; Information on the proportional effect for the variogram.